Like what you see when following this link:
It's cool!
That is done with jQuery. It's basically just animating the background color of the div itself. Assuming the background color of the div is set to orange to begin with:
$(".specialDiv").animate({ backgroundColor: '#ffffff' }, 1000);
As for setting the bg to orange to begin with, this is likely done as a result of the hash value in the URL. You can get that value with window.location.hash